References to Nietzsche will use the abbreviations below. References are by sections rather than by pages; these are uniform over different editions. For example, GM 2:9 refers to the Genealogy of Morals (in Kaufmann's Basic Writings), second essay, section 9; GS P.2 refers to section 2 of the (second edition) Preface of The Gay Science.
For Ecce Homo, a number of the chapters have the titles of Nietzsche's books. You may use either the chapter number or the abbreviation of the book title. For instance, you could cite section 2 of the chapter on Dawn (i.e., Daybreak) as "EH D.2" or as "EH VII.2". Here's a table of the chapter names/numbers:
If you're using The Will to Power, you may find the Concordance indexing the book to the standard editions of Nietzsche's collected works useful (available though online reserve).